Diverse cell movements during animal development contribute significantly to the establishment and maintenance of normal body plan and organogenesis. G protein signaling is one of many molecular genetic mechanisms that control these processes. Previously I showed the Ga12/13 are required for distinct cell behaviors that drive zebrafish gastrulation. In the mentored phase, I will work under supervision of Drs. Lila Solnica-Krezel and Heidi Hamm to continue characterizing the cell behaviors mediated by Ga12/13 signaling, to identify the downstream and upstream regulators of Ga12/13 during gastrulation. These studies will provide new insights into the molecular mechanism by which Ga12/13 modulate cell movements during embryogenesis. Knowledge and crucial techniques obtained during this period will provide me a solid foundation to launch my own independent research as proposed below. I have recently discovered that G protein signaling is also involved in migration of the progenitors of the gametes, primordial germ cells (PGCs). As in many other organisms, PGCs in zebrafish migrate from the position where they are specified towards the region where the gonad develops. It has been shown that this migration is governed by a chemokine G protein-coupled receptor, CXCR4b and its ligand, SDF1a. However, whether signaling proceeds through Gpy or Goc subunits, and their downstream effectors that are involved in PGC migration remain largely unknown. My preliminary results indicated that Gpy, Ga12/13 and probably Gaq are involved in the PGC movements. / hypothesize that PGC migration in zebrafish is mediated by diverse G protein signaling pathways probably through multiple receptors. I will employ a combination of genetic, cellular, pharmacological and biochemical approaches to test this hypothesis. In Aim 1,1 will characterize G(3y function in PGC migration, and test my hypothesis that Gpy transmit the SDF1a/CXCR4 signal. I will also identify the downstream effectors of Gpy that are required for PGC migration. In Aim 2, I will determine the roles of Ga subunits during PGC migration and investigate the involvement of cell adhesion and RhoA in this process. Based on my findings that multiple G proteins may be involved in PGC migration, my Aim 3 is to identify G protein coupled receptors other than Cxcr4b that regulate PGC migration, which may uncover unknown signaling pathways control PGC migration. Given that the signaling pathways of cell migration are conserved during embryogenesis, immune response and cancer cell metastasis, our study using an in vivo model with a vertebrate body plan will provide new insights into cell movement behaviors in normal development and disease.